Ch 26 Neuro exam and neuroanatomy Flashcards
1) sensorium and behavior
recumbency > brainstem, cervical cord, diffuse neuromuscular disease
Normal sensation depends on cerebrum and reticular activating system (located throughout the brainstem from the thalamus to medulla, to arouse the cerebrum).
consciousness and response to stimuli
Level of mentation (depression, obtundation, stupor) or quality (agression, pacing).
intracranial localization +/- cause as extracranial disorder (PSS).
2.Posture and Gait
posture, paresis, ataxia
differentaite from ortho (proprioception + reflexes)
- posture: intracracnial lesions can lead to decerebrate rigidity and decerebellate rigidity
- paresis: LMN vs UMN
LMS: flaccid, hyporeflex, short gait
UMN: spastic, hyperreflex, long gait with proprioceptive deficits
UMN pathway anatolmically similar to GP - ataxia: disruption of ascednding tracts
incoord, knuckling, hypermetric
general: gait associated with general proprioceptive ataxia has elements of both incoordination typified by hypermetria and upper motor neuron spasticity/rigidity.
ipsilateral (caudal to midbrain)
vestibular: loss of balance and orientation of the head
peripheral vestibular system (sensory receptors for special proprioception [balance] contained in the inner ear and/or cranial nerve [CN] VIII
central vestibular system (vestibular nuclei in the rostral medulla), ipsilateral upper motor neuron paresis and general proprioceptive ataxia typically are present
cerebellar: dysmetria, may have an intention tremor of the head
define:
decerebrate rigidity and decerebellate rigidity
opisthotonus,
intracranial lesions
disruption of descending inhibitory influence on the innervation of the extensor musculature.
opisthotonus: head and neck are extended.
Decerebrate: opisthotonus with rigid extension of the neck and all four limbs (midbrain or rostral cerebellar)
Decerebellate: severe cerebellar lesions, opisthotonus with extensor rigidity of the limbs but with the hip joints flexed.
3.postural
What is required for normal postural reactions??
What pathways are tested with postural reactons?
assess both proprioceptive and VMF (UMN and LMN, strength and coordination) of CNS and PNS
hopping,hemi,knuckling
conscious proprioceptive: [sensory] cerebral cortex
unconscious proprioceptive: the cerebellum)
proprioceptive > ipsilateral to the level of midbrain.
Subsequently, conscious projected to the contralateral thalamus and ultimately cerebral hemisphere.
4.spinal reflexes and tone
Patellar Tendon Reflex
biceps
withdraw
perineal
CTR
stereotypic response to stimulus independent of volition.
function of specific segments of the spinal cord is assessed, A normal reflex requires an intact afferent (sensory) and efferent (motor) arm of the reflex arc.
afferent= muscle spindle or Golgi tendon organ,sensory nerve, dorsal nerve root, and spinal cord segment.
efferent = lower motor neuron unit.
perineal reflex: pudendal n.
Cutaneous Trunci Muscle Reflex: C8-T1
preserved for one to two vertebral bodies caudal to the level of the spinal cord lesion
Cross extensor reflex: extension of opposite limb lesion cranial to site
pelvic reflex
Patellar Tendon ; femoral n (L4-6)
Pseudohyperrelfexia (loss of sciatic antagnosim dt L6-S1 lesion)
withdraw HL: sciatic nerve L6-S1
thoracic reflexes
biceps musculocutaneous nerve C6-C8
triceps radial nerve C7-T2
withdraw FL: musculocutaneous, median, ulnar, and radial nerves C6-T2
reduced with C1-C5 lesions 20%
What are the key upper motor neuron tracts which function in gait generation?
RuRet
Reticulospinal and rubrospinal tracts
Name the unconscious and conscious general proprioceptiv tracts
Faspi
Unconscious
- spinocerebellar tracts
Conscious
- Fasciculus gracilus (PL)
- Fasciculus cuneatus (TL)
sciatic nerve paralysis?
Plantigrade (tibial nerve dysfunction) and often walking on dorsal surface of paw (fibular nerve dysfunction) but can continue to bear weight due to an intact femoral nerve allowing stifle extension
Whats causes increased mucle tone in UMN lesions?
Much of the descending UMN influence provides for inhibition of extensor musculature. And UMN lesion therefore leads to loss of inhibition and overactivity of the extensors and hypertonia
6 steps in the stepwise approach to cranial nerve evaluation
Vision and PLR
Palpebral fissure and third eyelid symmetry
Eyeball position and movement
Vestibular function
Facial and trigeminal nerve function
Tongue and laryngeal-pharyngeal function
5.12 cranial nerves
I - Olfactory
II - Optic
III - Oculomotor
IV - Trochlear
V - Trigeminal (motor masticate, seonsory face)
VI - Abducens
VII - Facial (motor to face, taste tongue)
VIII - Vestibulocochlear
IX - Glossopharyngeal (pharynx)
X - Vagus (pharynx, larynx, and viscera)
XI - Accessory (larynx)
XII - Hypoglossal (motor tongue)
What is the two-neuron system of the autonomic nervous system?
A preganglionic neuron with its cell body within the CNS
A ganglionic neuron located in the PNS along with an effector muscle
Which spinal cord segments are home to the preganglionic sympathetic neurons which innervate the eye?
Where do they travel after leaving the vertebral column?
T1-T3
cranial thoracic cavity > brachial plexus >join vagus = vagosympathetic trunk carotid sheath > cervical ganglia
> cranial cavity, ultimately innervates the dilator musc of the pupil
6.nociception
three forms of cutaneous sensory receptors?
mechanoreceptors (touch)
thermoreceptors (temperature)
nociceptors (noxious stimuli)
Describe the noxious stimuli neural tracts
Noxious stimulus -> afferent impulse which enters spinal cord through dorsal nerve roots > bilateral tracts in lateral funiculi - > continue through medulla oblongata, pons, and midbrain to specific nuclei in thalamus -> relayed to somesthetic area of cerebral cortex
What is an autonomous zone?
CAUTION! individual patient variation is considerable
A cutaneous area innervated by a single nerve
autonomous cutaneous zones of the forelimb:
ulna
radial
musculocutaenous
Ulna n.
Palmer surface of paw (+ median n)
lateral aspect of digit V
Caudal antebrachium
radial n.
Dorsal paw and lateral antebrachium
musculocutaneous n.
Medial antebrachium
autonomous cutaneous zones of the hindlimb
fibular nerve
Dorsal paw
tibial nerve
Plantar paw
saphenous n (branch of femoral)
Medial aspect of limb
digit I
What are the 5 major regions of neurolocalisation?
Prosencephalon
Mid-to-caudal brainstem (midbrain, pons, medulla oblongate)
Cerebellum
Spinal cord
LMN/neuromuscular system
What kind of postural reactions will results from a unilateral proencephalic lesion?
Contralateral postural reaction deficits with normal gait
List some clinical scenarios which can cause confusion regarding the T3-L3 neurolocalistion
Schiff-Sherrington (disruption of ascending inhibitiroy axons of the border cells in the dorsolateral border of the ventral grey matter column of L1-L4)
> loss of UMN inhibition to FLs
Spinal shock - often with Schiff Sherrington (transient disconnect between the facilitatory descending UMNs and spinal cord motor neurons
> LMN signs in the HLs
What does a LMN unit consist of?
Alpha-motor neuron (nerve cell body) in ventral grey matter
Ventral nerve root
Spinal nerve
Nerve plexus
Named nerves of the limb
NMJ
Muscle
What are the three braod categories of LMN disease?
Neuropathy
Myopathy
Junctionopathy
What is the most common sign associated with diffuse CNS disease?
What are some differentials?
Fine, whole body tremor
DDx: disorder of myelin formation, meningitis, metabolic disease, degenerative disease (kysosomal storage disease), toxicity
